The original Kroyer process and Kroyer machine are disclosed in the U.S. Pat. Nos. 3,581,706 and 4,014,635 to Karl Kristian Kobs Kroyer. In those prior art patents, fiber is passed through a static wire screen by using downward air flows and rotating paddles or impellers in an enclosed distributor or distributor head. After the fiber has passed through the static wire screen, it is formed on a moving forming-wire screen. The fiber is directed to the moving forming-wire screen by producing a suction under the forming-wire screen and particularly directly beneath the distributor. The front end of the distributor is the end which receives the moving forming-wire screen and the back end of the distributor is the end which delivers the moving forming-wire screen with fibers forming a web thereon. The forming area is closed off by sealing rolls on the front and back ends of the distributor and by side seal deckles.
As the forming-wire screen speed of a Kroyer machine increases, the sealing rolls build up electrostatic charges causing the fibers to stick to the rolls which disrupts the already-formed web. The sealing rolls perform well at screen speeds up to about 200 feet per minute, but their performance degrades as the speed increases so that by the time the moving forming-wire screen is moving between 500 and 700 feet per minute the formed web is totally disrupted by the sealing rolls.
Gaps between the sealing rolls and the side deckles also allow air to pass into the forming area from the outside atmosphere, disrupting the web edges. The disrupted edges then jam the next sealing roll with fiber locking into the gap between the sealing roll and the side seal deckle.
When two or more distributors, each having a pair of sealing rolls, are used, the fiber web or mat lifts off the wire at higher speeds because of windage and the fact that there is no vacuum under the moving forming-wire screen between the exit sealing roll of one distributor and the entrance sealing roll of the next distributor to hold the web down.
In a patent application filed concurrently herewith by Dennis L. Mielke, entitled APPARATUS FOR THE DEPOSITION OF DRY FIBERS ON A FORAMINOUS FORMING SURFACE, there is disclosed and claimed the concept of using a common tunnel for the forming area of two Kroyer type machines with a space between the machines. Perforations are made in the top of the tunnel between the machines to minimize turbulence in that region and in the baffle below the moving forming-wire screen in the region between the Kroyer machines to hold the web on the forming-wire screen. Such a design has run successfully at 1,000 feet per minute with good web formation. However, in the areas between the distributors there occurred some air turbulence which resulted in fiber building on the sides. In unperforated areas of the top of the tunnel, when the build-ups became large enough they fell onto the web producing localized spots of high basis weights and high opacity which were readily noticeable. In addition, such localized spots were proved to pick in the embossing process leading to a poorer running sheet.
Further, the pulling of air through the web to hold it down in the areas between distributors is an energy wasteful process.
The following issued patents in addition to the above-mentioned Kroyer patents, are representative of the state of the art:
Austrian Pat. No. 220,446 to Weyerhauser Timber Co. teaches a plurality of non-Kroyer type distributors for laying fibrous material.
U.S. Pat. No. 3,825,381 to Danning teaches a plurality of non-Kroyer type distributors for forming airlaid wood fiber webs.
U.S. Pat. No. 3,645,457 to Greten, et al teaches two non-Kroyer type distributors depositing wood chips on a belt.
U.S. Pat. No. 3,598,680 to Lee teaches two non-Kroyer type distributors depositing fibers on a belt.
U.S. Pat. No. 3,080,617 to Lytton teaches a plurality of non-Kroyer distributors depositing consecutive layers of fibers on a belt.
U.S. Pat. No. 3,071,822 to Meiler teaches a plurality of non-Kroyer felters delivering fibers to a belt.
U.S. Pat. No. 2,165,280 teaches a plurality of non-Kroyer blowers delivering fibers to a belt.